Distributed System, Computer Program Product and Method

1. A computer-implemented method, comprising: generating an access set, which is a set of database entries to be accessed by each of a plurality of transactions, which are to be executed for a database of replica of common data in each of a plurality of member nodes that each store the database; and generating a batch that is to be executed by each of the plurality of member nodes and includes two or more transactions that lack an access conflict, based on the access set of each of the plurality of transactions to be executed; performing parallel execution of any of the plurality of transactions included in the batch including performing speculative execution for remaining transactions among the plurality of transactions to be executed to generate a next batch; performing a process to reach a consensus for the batch with the plurality of member nodes; and committing the two or more transactions included in the batch, in response to a consensus being reached for the batch among the computer and the plurality of member nodes.

2. The computer-implemented method according to claim 1 , wherein performing the parallel execution includes performing speculative execution of the plurality of transactions to be executed, and wherein the generating the access set includes generating the access set of each of the plurality of transactions to be executed, based on results of the speculative execution.

3. The computer-implemented method according to claim 1 , wherein the speculative execution is started after the two or more transactions included in the batch have been committed.

4. The computer-implemented method according to claim 1 , wherein the speculative execution is started before the two or more transactions included in the batch have been committed.

5. The computer-implemented method according to claim 4 , wherein performing the parallel execution includes, when performing the speculative execution of the remaining transactions to generate the next batch, speculatively reading data scheduled to be written to the database by uncommitted transactions in the batch.

6. The computer-implemented method according to claim 4 , wherein performing the parallel execution includes, when performing the speculative execution of the remaining transactions to generate the next batch, uses results of a previous speculative execution for transaction that did not have a write-read conflict with other transactions that had already been executed to generate the batch or a previous batch.